Astrophotography with an inexpensive 80mm f/5 refractor

Eight years ago I purchased a Meade 80mm f/5 refractor brand new for $90.  The specific retail package was advertised as the Meade "Adventure Scope".  I discarded all the cheap accessories and upgraded the optical tube with a GSO Crayford focuser and some tube rings and dovetails.  This scope is now going to be loaned to the Lookout Mountain Observatory Association in Del Norte for the purpose of developing a way to electronically display images in near realtime at public events.  Before it leaves home, however, I wanted to take some pictures to establish a baseline expectation for what might be achieved.

Here is a picture of the scope from the retail packaging: 

And here is what the new configuration looks like, with an ASIAIR mini control module and an ASI294MC-Pro cooled astro camera:

 The sky was clear enough on Thursday night (02 July) to take some photos using this scope with an Olympus E-M5iii camera, riding on a ZWO AM3 mount.  The moon was rising, though still hidden behind the ridgeline of Snowshoe Mountain.  Because of the rising moon, sky brightness was only 20.5 mpsas.

This scope is an achromatic doublet, which comes with two flaws that affect astrophotography.  The first is field curvature, and the second is chromatic aberration in the form of purple fringing.  To mitigate these problems, these images were obtained with a field flattener and a UV/IR cut filter. 

The sensors in the E-M5iii and ASI294MC-Pro are nearly the same size, so these images should be representative of what can be achieved with the astro camera. 

All of the following images are single exposures of between 30 to 60 sec. 

M8, the "Lagoon Nebula"

 Messier 8 (M8) is in the constellation Sagittarius in the heart of the Milky Way. The cluster in the lower left of this image is the globular cluster NGC 6544, about twice as far away (9800 ly).

Star cluster M21 (near center) and M20, the "Trifid Nebula" in Sagittarius.

 

Open cluster M23 in Sagittarius

Open cluster M25 in Sagittarius

Globular cluster M22 in Sagittarius

Open clusters NGC 6716 and Collinder 394 in Sagittarius

The scope was also used to view a few of the nearest stars.  

Barnard's Star in Ophiuchus

 Barnard's Star, at 5.96 ly, is the second closest star system after the Alpha Centauri system.  It is a magnitude-9.5 red dwarf star.

Ross 154 in Sagittarius

 Ross 154, at 9.71 ly, is the seventh closest star system.  It is a magnitude-10.5 red dwarf star in Sagittarius.

 

61 Cygni

The double star 61 Cygni (in Cygnus) is the 14th closest system, at 11.4 ly.  The two slightly uneven components are each about 2/3 the size of our Sun.  

July 3rd Aurora

 The northern sky seemed unusually bright last night.  The camera revealed that an auroral display was in progress.  The color was not visible to the eye. These images were obtained with a Sony A7iii + Nikon Ai-S 20mm f/2.8 lens.  The time was about 11:30 pm MDT.

The smoke layer on the horizon is from the Gold Mountain fire near Ouray. 

 

There are some large sunspots about to rotate out of view.  Solar activity from this region is probably the cause of this auroral display.

Meade 80mm f/5 refractor + Lunt Solar Wedge.

 The Milky-Way view toward the south shows no aurora, but the eastern sky is starting to brighten with moonlight.

 A view of the Summer Triangle reveals the pink auroral glow on the northern side of the frame.

 

Strawberry Moon

 The full moon of June, known as the "Strawberry Moon", occurred on 29 June.  The Moon reached apogee on 28 June, so this full moon is smaller than average, making it a "micromoon".

The following images were all obtained with an Apertura 60mmED f/6 refractor.

rising through the trees on Snowshoe Mountain, 10:53 pm

 

The next day the same telescope (with a solar wedge) was used to capture an image of the sun.  

 The Sun and Moon images overlaid illustrate the smaller-than-average full-moon size:

 

Near-Earth asteroid 1997 NC1

 Asteroid (152637) 1997 NC1 is a near-Earth asteroid that just made a close pass on 27 June.  Its closest approach was just under seven times the distance to the moon. Recent data show that it is a peanut-shaped object about 1-km long.  Because of high winds and a bright moon, trying to capture an image on the 27th (Saturday) did not seem very appealing.  However, last night (28 June) was much calmer and the moon remained hidden behind the flank of Snowshoe Mountain until just after 10 pm.

 The lens used was a Rokinon 135mm f/2 mounted on an Olympus E-M5iii camera.  The bright moonlight meant that exposures were limited to 5 sec.  Two images were obtained, separated by 108 seconds.   The movement of the asteroid is easily visible.  It was moving about 0.6°/hr.

 

Asteroid (152637) 1997 NC1 (circled).  1-deg wide field.

Animation of two exposures 108-sec apart.

The star at the center of the above images is HD 151721 in Scorpius.

Shortly after these images were obtained, the nearly-full Strawberry Moon rose over the southern ridgeline of Snowshoe Mountain.

 

Strawberry Moon

Antares and the globular cluster M4 in the bright moonlight.  5-sec exposure.

The Flying Star in Cygnus

 The fourteenth-closest star system is the double star 61 Cygni.  At a distance of 11.4 ly, this pair was nicknamed the "Flying Star" by Giuseppe Piazzi in 1792 because of its high proper motion of about 5 arcsec per year.  This was also the first star system to have its distance measured by trigonometric parallax, by Friedrich Wilhelm Bessel in 1838. The two stars, which are separated by 32 arcsec,  have magnitudes of 5.2 and 6.0 and a combined magnitude of 4.8.  This makes the star technically visible to the naked eye, under dark skies with good eyesight.

 I photographed the star Monday night, in the light of the first-quarter moon, using three lenses: Panasonic Leica 25mm f/1.4 (with softon filter), Rokinon 135mm f/2, and Asto-Tech AT80EDT refractor.

The constellation Cygnus and 61 Cygni (circled). Leica 25mm

 

61 Cygni resolved with the Rokinon 135mm lens

61 Cygni A + B.  AT80EDT refractor

The Milky Way core rising over Snowshoe Mtn.  Leica 25mm

The source of the blue sky, the first-quarter moon:

AT80EDT refractor

 

A nearby double star: Struve 2398

 Of the fifteen-nearest star systems, seven — almost half — are double or triple stars.  The fifteenth-closest star system is Struve 2398, at a distance of 11.49 ly.  It consists of two red-dwarf stars with magnitudes 8.9 and 9.7.  Struve 2398 is in the northern sky in the constellation Draco.  The image below shows its location relative to the Little Dipper.

Struve 2398 (circled), the 15th closest star system.

 The Little Dipper is on the left side of the frame, with Polaris in the lower-left corner.  A Panasonic Leica 25mm f/1.4 lens with a Hoya Softon filter was used to obtain this image in moonlight (hence the blue sky) on Saturday night.

A Rokinon 135mm f/2 lens provides a closer view:

Struve 2398 (circled). Rokinon 135mm f/2.  North is up.

Finally, an Astro-Tech AT80EDT 80mm f/6 telescope was used for an even closer view that shows this double star resolved into its two components:

Struve 2398 (middle). 2x enlargement.

 This image is a stack of three  exposures.  The two stars are separated by about 12 arcseconds.   The star toward the left of the frame is an unrelated background star.

On the same evening, even though the moon was up, I used the Leica 25mm lens to capture a shot of Scorpius rising over the southern end of Snowshoe Mountain:

 

Moon, Mercury, Milky Way

On Wednesday evening, 16 June, Mercury was still visible and accompanied by the crescent moon during twilight.

Mercury (circled) and the Moon.  Olympus 40-150mm f/4.

 

Mercury (center) 1:1 crop.  Olympus 40-150mm

Near midnight, long after the moon had set, I imaged the Milky Way with an OM 20mm f/1.4 lens.

3x3 median digital filter

 

Summer Triangle, 3x3 median digital filter

These are the same two scenes with a physical Hoya Sparkle-6 filter:

 

A more southerly view:

 The layers of green and purple airglow are mostly invisible to the unaided eye and simply present as a vague brightening toward the horizon.  When strong airglow is present the sky near the horizon is typically about 0.4 mpsas brighter than directly overhead.